package oj;

import list.LinkedList;

public class ChkPalindrome {
    public boolean chkPalindrome(ListNode A) {
        if(A == null) {
            return true;
        }
        ListNode fast = A;
        ListNode slow = A;
        while(fast != null && fast.next != null){
            fast = fast.next.next;
            slow = slow.next;
        }
        ListNode cur = slow.next;
        while(cur != null){
            ListNode curN = cur.next;
            cur.next = slow;
            slow = cur;
            cur = curN;
        }
        while(A != slow){
            if(A.val != slow.val){
                return false;
            }
            if(A.next == slow){
                return true;
            }
            A = A.next;
            slow = slow.next;
        }
        return true;
    }
}
